1. Field
The present disclosure relates to the field of the manufacture of a mold for a tire comprising a plurality of cavities which are able to mold closure devices in one or more groove(s) of this tire. More particularly, the disclosure relates to the manufacture of a mold able to mold closure devices fixed to the lateral walls of the grooves.
2. Description of Related Art
Document WO 2010146180 discloses a vulcanizing mold for a tire comprising a plurality of molding elements. Each molding element is delimited by two edges in contact with two other adjacent molding elements so that once the molding elements are in contact with one another, all of these molding elements together allow all or part of the tread of the tire to be molded.
Each molding element comprises a base and a bar projecting from this base. The base is intended to mold the tread surface of the tread of the tire and the bar is intended to mold a groove in the tread of this tire, i.e. a cut of a width greater than or equal to 2 mm.
It is known that, in the contact patch in which the tread is in contact with the road surface, each groove forms a resonance tube with this road surface. This resonance tube amplifies the running noise of the tire, and this may be unpleasant for people situated inside the vehicle and/or outside this vehicle.
In order to limit the intensity of this resonant noise, it is known practice to provide the grooves with special closure devices also referred to as “flexible walls”, or “flaps”. These closure devices take the form of thin blades. These blades partially close off the cross section of the grooves when the tire is running on a dry road surface. When it is running on a wet road surface, the blades flex under the action of the flow of water, so that this water can be removed from the contact patch. The grip of the tire on the road surface is thus maintained even when running under severe wet conditions.
There are various types of devices for closing a groove. For example, document WO 2010063749 discloses closure devices which are fixed by their base to a bottom of a groove. It has been found that the flexibility of these devices changes over time. Thus, with tire wear, the height of these closure devices decreases, thus causing their rigidity to increase. These closure devices may therefore ultimately prevent water from circulating properly in the groove.
In order to improve the operation of the closure devices on a wet road surface, document FR2715891 has proposed closing the cross section of the groove using two closure devices belonging to one and the same transverse plane and each one covering approximately half the cross section of this groove. These closure devices are fixed respectively to lateral walls of the groove and not to the bottom of this groove. Thus, with tread wear, the region of attachment of each closure device to the associated wall of the groove decreases. The flexibility of the closure device is maintained over time, or even increased, until a certain degree of tread wear is reached.
However, in order to mold these closure devices into a groove, it is necessary to make slots in the lateral faces of a bar of a mold, it not being appropriate for these slots to open onto the upper surface of this bar. Now, creating these slots with the required degree of precision is accompanied by a great many difficulties.
FIG. 1 schematically depicts a perspective view of a known embodiment of a molding element 1 that can be used for molding a closure device fixed to a lateral wall of a groove.
The molding element 1 comprises a base 3 and a bar 5 projecting from the said base 3. The base 3 and the bar 5 are in this instance formed as one from the same substance and made of a material of the aluminium type.
More particularly, the base 3 comprises a molding surface 7 intended to mold part of the tread surface of a tire. The bar 5 for its part comprises an upper face 9 intended to mold the bottom of a groove and two lateral faces 11, just one of which is depicted here. These lateral faces 11 project from the molding surface 7 of the base 3 and extend along the length of the bar.
More specifically, the bar 5 comprises a recess 15. This recess is intended to accept raw rubber for molding a closure device in a groove of a tire. The recess 15 in this instance opens onto one of the lateral faces 11 of the bar 5 and onto a contact edge 17 of the molding element 1. By contrast, the recess 15 does not open onto the upper face 9 of the bar 5.
FIG. 2 shows an assembly of two molding elements 32a, 32b according to the embodiment of FIG. 1. More specifically, FIG. 2 is a view in cross section of this assembly on a plane substantially parallel to the molding surfaces 39a, 39b of the molding elements 1a, 1b. 
Assembling the two molding elements 32a, 32b forms two cavities 33a, 33b which are offset from one another along the length of the bar 35, each cavity 33a, 33b opening respectively onto one of the lateral faces 37a, 37b of this bar 35. More specifically, each cavity 33a, 33b is formed by a recess belonging to one of the two molding elements 32a, 32b, this recess being delimited by a contact edge belonging to the other molding element 32a, 32b. 
Now, such an assembly limits the design options for the closure devices. This is because with the assembly of FIG. 2, it is not possible to mold closure devices which are offset along the length of the bar and exhibit a certain overlap (“overlapping”) as is notably depicted in document JP3276802, in FIG. 10 (A).